Critically evaluate of methods of purification to obtain pure rare metals.
Obligatory stage of technology is the production of pure chemical compounds, rare metal separation from accompany it impurities. To solve this problem is widely used extraction, ion exchange, distillation and other methods. From pure chemical compounds by electrolysis and metallothermy obtain metal.
For the technology of rare metals are characterized by the need for refining the resulting metal. To this end, widely used vacuum distillation, iodide refining, crystallographic methods of cleaning, etc.
One of the main limits is to obtain compact and alloy ingots in a convenient form for the subsequent machining, producing semi-finished or finished products.
In technology of rare elements ion-exchange chromatography has proved particularly useful when splitting a large group of chemically similar rare earth metals. It is possible to identify four main areas of application of ion exchange in hydrometallurgy: 1) the enrichment and concentration; 2) separation; 3)purification; 4)the disposal of effluent.
Extraction methods in the technology of rare metals used for purification and for separation of similar properties of rare elements. Application of extraction allows for the continuous of high-performance process, it is easy to control and automation.
Metallothermy - a process of recovery of metals from their compounds with other metals, are chemically more active at high temperature. Sometimes here also includes non-metals recovery processes.
Metallothermic reduction reaction can be represented by the equation, wherein X - anion, ∆Н - thermal effect
Electrolysis is one of the main methods of obtaining rare metals, alloys and refining the crude metal.
Electrolysis is the decomposition of the electrolyte by a constant electric current, which is accompanied by the formation of new substances. On the electrodes occur the oxidation reaction – recovery: the anions at the anode give up electrons and are oxidized and the cations are recovered at the cathode.